Hello thanks to Baz, and all. I did eventually manage to make one but will order a 'propper' one, the crosman one seems to fit the bill.
It has a most parculiar piercing arrangement ( well it is to me) a brass coloured washer with a dome in the middle which has a number of claws. The piercing pin (which is solid) fits through the claws, this rests in a recess in the face of the valve, a hole offset from the centre line of the face goes into the valve chamber.
The seal fits over the brass washer with a hole for the pin. There is a retaining collar for the seal. The shape of the seal is a bit of a guess because there is hardly anything left of the old one.
Sorry for the delay in any replys,
had to finish rebuilding the lathe,
had 2 power cuts,
cul-de-sac with 3 bus size vehicles due to inpending sewer collapse.
All quiet really!!
When it is completed properly will pop back.
ATB.
Geoff.